Electrolytic cell



Jun 13, 1933.

F. H. ESTES ELECTROLYTIC CELL Filed Oct. 23, 1929 um-(4446 a M tic shock impulses.

Patented June 13, 1933 UNITED STATES PATENT OFFICE PHILLIP H. ESTES, OF RUTHERFORD, JERSEY, ASSIGNOR TO THE WESTERN UNION TELEGRAPH COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTROLYTIC CELL Application filed October 23,1929. Serial No. 401,783.

This invention relates to a device for protecting electrical acoustic elements from shock due to over-voltage impulses transmitted over the connecting circuits.

Heretofore, electrolytic cells consisting of one lead electrode and one tantalum electrode dipped into a solution of sulphuric acid have been employed for protection against acous- Cells of this ty e have everal disadvantages, namely: (1) 'lhe acid evaporates below the level of the ends of the electrodes, and, since in order to keep the electrolytic capacitance at a minimum it is necessary to have only a very short length of such electrode exposed to the acid, the evaporation of the solution is quite serious; (2) In time, a film of lead sulphate forms on both electrodes and changes the characteristics of the cell, sometimes entirely stopping its aclon; and (3) Due to the nature of the materials, it is necessary to employ two cells in each protector connected in oppositedirections to obtain two-way o ration.

An object of my invention is to devise an "nproved electrol tic cell in which evaporation of the electro yte' does not impair the operation of the cell untilsubstantially all of the electrolyte is eva orated.

A further object o my invention is to de- 1 Ise an electrolytic cell in which the capacitance between the electrodes is reduced to a minimum.

Another object of my invention is to devise an electrolytic cell havlng only two electrodes and being capable of two-way operation as a voltage protector.

Still another object of my invention is to devise an electrolytic cell having a low overvolta e point at which the resistance of the. fianges from a high value to a relatively 'll (3 low value.

My invention is illustrated in the accompanying drawing in which:

Figure 1 is a sectional view illustrating one I arm of my invention in elevation;

Figure 2 is a view of the lower side of Figure 1;

a Figure 3 is a sectional view of Figure 2 taken along the line 3-3;

Figure 4 is a plan view of Figure 1; and

Figure 5 is a circuit diagram illustrating the manner in which the cell is employed.

Referring to Figure 1, 1 indicates a cup of insulating material, such as hard rubber, containing a quantity of sulphuric acid 2. Embedded in the bottom wall of the cup 1 is a pair of spaced electrodes 31; and 3b, preferably made of, platinum. The bottom of the cup is provided with a recess 1a in which are mounted two detachable connecting prongs 4a and lb, the construction being similar to that of an ordinary electric light plug connector. ed respectively to the prongs 4a and 4b, and the upper ends of electrodes are arranged flush with the inner surface ofthe bottom of'the cup 1, thereby exposing a minimum area to the electrolyte and reducing the capacitance between the electrodes to a minimum. The cup 1 is provided with a screw 'cap 5 in which is located a ball valve 5a, which prevents the admission of dirt and extraneous matter, allows the escape of gases, and also prevents excess evaporation of the acid. The ball valve 5a is seated in a central aperture in a washer 5b carried by the cap 5, and extends into a slotted opening 5c formed in cap 5.

One application of my invention is illustrated in Figure 5, which shows the protector cell 1 connected in shunt to a telephone receiver 6 in an ordinary common battery telephone system. Operation of the cell in the Electrodes 3a and 3b are connectarrangement shown in Figure 5 is as follows:

The cell passes only a very minute current for impressed voltages less than two and one-half volts, but for potentials above this point, current passes through the cell very freely. Since both electrodes are made of platinum in contact with sulphuric acid, the cell Will operate in both directions. For the weak incoming signals transmitted over the telephone line from a distant station, the resistance of the cell is very high, and substantially the entire signal current flows through the receiver 6, and substantially no current is absorbed by the cell 1. For incoming impulses having voltages greater than the overvoltage point of the cell, the resistance of the cell is lowered to substa ntially short-circuit the receiver and prevent acoustic shock to the user of the telephone. It will also be noted that in case the talking currents generated by the local transmitter exceed the over- 5 voltage point of the cell, the cell will act to shunt these currents around the receiverand thereby prevent side tone noises in the receiver.

The improved cell which I have devised has an over-voltage point at two and one-half volts, whereas thecommonly used leadtantalum cell has an over-voltage point at substantially three and one-half volts. The underlying theory of the over-voltage point is that a certain voltage is necessary between an electrode and the electrolyte before electrons will commence to flow. This voltage varies with the chemical composition of both the electrode and the electrolyte. The com- '29 bination of platinum electrode and sulphuric acid electrolyte employed in my improved cell produces a lower over-voltage than any prior cell and, therefore, affords better protection against over-voltage impulses. Furthermore, since platinum is a comparatively inert metal, the electrodes in my improved cell will not sulphate readily at ordinary temperatures. Thus, I obtain a cell which is practically free from changes due to the chemical action of the cell when not in operation. It will be noted that since the electrodes are inserted into the bottom of the cell, evaporation of the electrolyte will not afi'ect the operation of the cell unless substantially all of the electrolyte is evaporated.

It will be obvious to those skilled in the art that changes in detail arrangement may be made without departing from my invention in its broadest aspect.

40 I claim:

1. An electrolytic cell comprising a cup of insulating material containing sulphuric acid, and a pair of spaced electrodes comprising platinum rods extending through the bottom of the cup with their upper ends flush with the inner surface of the bottom of the cup and in contact with the sulphuric acid.

2. An electrolytic cell comprising an electrolyte containing sulphuric acid and a pair of platinum electrodes having an exposed surface area coinciding substantially with a cross-section of the electrodes and spaced from each other to cause a break-down voltage at substantially two and one half volts therebetween.

3. An electrolytic cell comprising a cup of insulating material, and a pair of spaced platinum electrodes extending through the wall of the cup with their inner ends substantially flush with the inner surface of the wall.

In testimony whereof I affix my signature.

PHILLIP H. ESTES. 

